The present invention relates to a structure of optical image detecting device with optical image differential capability which is comprised of a plurality of lens assemblies in quantity and angle positions corresponding to the optical images to detect, each optical lens of which has a thickness smaller than the shaded projection of each optical image but a maximum diameter larger than the shaded projection of each optical image.
Optical image detecting technique is very important in the field of precision technology. In the arrangement of single light source, single variation and single receiver, a receiver is simple in structure and designed to detect the availability of light ray (on/off of a light source; or pass or blocking of light beam). When multiple light sources, multiple variations and multiple receivers are required, the relative arrangement of the light sources, the mode of variations and the receivers becomes more complicated. For two or more optical image changes multiple light sources are used, i.e. an additional light source and a specific receiver are provided for each change. In order to prevent from interference of optical image against each other, light sources of different wavelength are commonly used. Therefore, a receiver is designed to receive signal from an optical image of specific wavelength. The common disadvantage of this optical image differential method is its complicated structure and expensive manufacturing cost. Because it is inexpensive to manufacture a light source of specific wavelength. In order to control receivers to respectively act on a specific light beam of a specific wavelength, the design of the posterior electronic circuit becomes more complicated. Further, the more the light sources are used, the bigger the space is occupied. Optical image detecting technique has been widely used in various fields. Electro-optical mouse is an example. In the conventional optical mouse, two separate light sources are generally used for differentiating the motion in the X direction from the Y direction on the pad, i.e. one to reflect on the grid of lines in the X direction and the other to reflect on the grid of lines in the Y direction. The wavelength of the first light source is different from the second source. Corresponding to the two separate light sources, two receivers (detectors) are provided inside the optical mouse to respectively detect the image from the illuminated surface. Upon detection of reflected image, the receivers (detectors) provide "Hi" or "Lo" output, according to the shading of detected image, to a posterior electronic circuit for counting line crossings (shading change) so that observed detector motion on the surface in X, Y can be made to correspond to cursor motion for a video display. This arrangement cannot eliminate the aforesaid problems of complicated structure and expensive manufacturing cost.